A hybrid electric vehicle relies upon two power sources for delivering power to vehicle traction wheels. One power source typically is an internal combustion engine and the other power source is a battery and a motor, together with a generator. In a so-called power-split hybrid electric vehicle powertrain, a generator is mechanically coupled to the engine and is electrically coupled to the battery and the motor. For example, in U.S. Pat. No. 7,467,033, a split power delivery path is established by a simple planetary gear unit whereby the generator is connected drivably to the sun gear of the planetary gear unit and the engine is connected to the carrier of the planetary gear unit. The ring gear of the planetary gear unit is mechanically connected to the motor. Although a split power hybrid electric vehicle powertrain is capable of embodying the present invention, other types of hybrid electric vehicle powertrain architectures may embody the invention as well, including non-hybrid powertrains in which an internal combustion engine is a power source.
Although known hybrid electric vehicle powertrains provide a significant improvement in overall powertrain fuel economy and reduce undesirable exhaust gas emissions compared to conventional powertrains, there is a potential for still further improvement in fuel economy by making adjustments in factors such as driver style, driver behavior and driver preferences. This may be done by providing appropriate feedback to the driver with regard to adjustments that affect fuel economy. The feedback may be in the form of visual indicators or displays.
A hybrid powertrain typically includes a vehicle control system that coordinates power distribution from each power source to achieve an optimum balancing of torque, speed and power from each power source. The control system includes an engine controller, a transmission controller, a high voltage battery controller, a regenerative braking system, and a high voltage battery. A vehicle system controller performs an overall vehicle system coordination and oversight by communicating with several subsystem controllers. The vehicle system controller manages and coordinates the driveline functions to satisfy the driver's torque request and to balance energy flow to and from the subsystems. A real-time advisory system can provide direct advice to drivers regarding optimal accelerator pedal and brake pedal inputs to the vehicle system controller.